An NDA may be submitted for a direct-to-OTC drug product. However, many FDA-approved OTC drug products (i.e., OTC products that have an approved NDA) begin their lifecycle as NDA-approved prescription drugs, and then eventually switch to OTC status under the NDA provisions.
This is commonly referred to as an Rx-to-OTC switch, and while the process for obtaining an Rx-to-OTC switch is outside the scope of this training, FDA has numerous sources for information on the topic, which you can access under the Resources tab.
Historically during the early implementation of the OTC Drug Review, many former prescription drugs were switched to OTC status. However, Rx-to-OTC switches today primarily occur through the NDA procedures.